Magnetic Field dependence of specific heat in Clinoatacamite Cu ₂Cl(OH)₃

We have measured the magnetic field dependence of the specific heat up to H=6 T in a geometrically frustrated magnet, clinoatacamite Cu2Cl(OH)3, with the corner-sharing tetrahedron structure of the Cu²⁺ ions. At H=0 T, the specific heat exhibits two anomalies at T₁=6.2 K and at T ₂=18.1 K T₁ shows a reentrant behavior in the T - H phase diagram, while T₂ shows a gradual decrease with increasing magnetic fields. The field dependence of T₁ and T₂ may reflect different aspects of two transitions. The transition at T₁ is related with the two dimensional nature of the kagome antiferromagnets which are weakly coupled via Cu²⁺ ions at the triangular sites located in between the kagome layers, while that at T₂ represents the feature in a conventional long-range ordering.